The decoration of textile fabrics and related flexible materials by transferring coloured patterns from an extensible support previously printed with an appropriate design is well known. The methods in use may be put into three distinct categories:
(a) sublimation transfer using heat volatile dyes and components PA1 (b) solvent transfer using a solvent to enable the dyes to diffuse from the printed design on the extensible support to the textile fabric. PA1 (c) melt transfer using heat and pressure to melt a design onto the fabric.
British Patent No. 349,683 (British Celanese Ltd) describes a method falling into the first category in which a non-polar or disperse dye is volatilised from a paper support in contract with a textile material at elevated temperatures. Many patents describe improvements to the processes of manufacture of the decorated paper support. In particular British Patent Nos. 1,190,889 (Trentesaux--Toulemonde S.A.), 1,342,304 and 1,391,012 (Sublistatic Holding S.A.) describe flexible decorated paper supports carrying disperse dyes which vapourise between 160.degree. C. and 220.degree. C. in the presence of heat stable binder for the transfer printing of synthetic textile materials. The method is characterised by a slow transfer of dye from the paper dependent upon the volatilisation and diffusion of the dye so that even at the extremes of usable temperatures near to the melting point of the synthetic textile material transfer requires 30-60 seconds. The slow transfer requires that the decorated paper and the textile be held in contact without relative movement all through the transfer period. This requires the use of special costly machines such as that described in British Patent No. 1,227,681 (Hunt and Moscrop Ltd). In addition both paper and textile fabric must be selected or pretreated so that they do not show more than a limited amount of relative dimensional change during the transfer operation. The system is characterised by considerable commercial and technical attraction but possesses none the less serious inherent disadvantages. The sublimable dyes may diffuse into the flexible paper support instead of into the textile fabric during transfer giving incomplete transfer. The rate of transfer of different dyes is not the same and the sensitivity of transfer rates to the temperature and contact pressure leads to difficulties of control of the process. The process is by its nature restricted to the use of volatile dyes and hence to the more readily sublimed disperse dyes. This leads to a restriction in the application of the process to synthetic fibres notable polyetheylene terephthalate fibres since the fastness achieved on other kinds of synthetic materials is poor. Numerous attempts have been made to overcome these shortcomings. U.S. Pat. No. 3,782,896 (Defago et al) describes the use of a restricted range of disperse dyes which are sublimable and carry substituents capable of reacting with isocyanates to give fast washing colourations. Among other variations masked isocyanates are described which may be mixed with the dyes in the decorating material and which react with the dye after it has transferred to the textile material. Transfer of both dye and its fixing agent is slow and the requirement that the isocyanate reagent react with the dye on the fibre rather than on the transfer paper increases the time necessary so that 60 seconds is a required transfer/fixation time. British Patent No. 1,445,201 (BIP Ltd) describes the treatment of textile fabrics prior to or after sublimation transfer printing with an alkylated melamine formaldehyde resin of appropriate formula. In this way it is claimed good results may be obtained on a variety of fabrics. This process offers a significant disadvantage in requiring a pre - or post impregnation and drying process as well as suffering from the deficiencies of slow transfer, sensitivity to processing variables which it shares with the Defago process. Another means of extending the applicability of sublimation transfer has been described in U.S. Pat. No. 3,995,992 (Ciba Geigy) whereby special derivatives of basic dyes are prepared and used for the sublimation transfer printing of acrylic fibres.
The use of solvent transfer procedures avoids one of the serious limitations of the sublimation procedure i.e. the need for sublimable dyes and the restriction to textile fibres printable with such dyes. Instead of requiring the dye to migrate through the vapour phase in such procedures, the space between the decorating material and the textile is filled with a solvent in which the dyes are soluble and the dye diffuses through it. Such a process is taught in U.S. Pat. No. 1,965,257 (A.B. Poschel). An improved form of the procedure is described in workable detail in U.S. Pat. No. 2,583,286 (Albini Colombo). Before contacting the decorating material the textile is moistened and the paper and moist cloth are passed through a heated calender. The dyes used were applied to the transfer paper or decorating material from an ink based on linseed oil by standard printing procedures. The ink media are transferred to the textile material by the process so that as a final treatment the textile material has to be washed with hot water to remove unfixed dyes and also treated with fat removing solvents such as trichloroethylene. The process offers rapid transfer i.e. during the very short period of time of contact in the heated calender but suffers serious disadvantages in relation to the efficiency of fixation of the dyes in the absence of any dyeing assistants e.g. acids, bases etc, the need for a pre wetting treatment and the complex washing off procedure using solvents. In another version of solvent transfer British Pat. No. 1,284,824 (Dawson Holdings) describes the use of decorated paper transfer materials held in contact with specially pre-treated fabrics and heated in a moist condition to allow the dye to transfer to the fabric. Unfixed dye and the pre-impregnation solution are then removed by washing. A simpler process is described in British Pat. No. 1,243,223 (Ciba Geigy) which applies the decorated material to the textile and subjects the composite to pressure at an elevated temperature under humid conditions. Necessary ingredients for aiding the fixing of the dyes on the textile fabrics may be included in the decorating inks. Transfer occurs without the use of any binder for retaining the dye on the fabric but transfer is slow i.e. between 10 seconds and 5 minutes. At the end of the humid treatment washing off is essential to remove surplus dye not taken up by the textile. Melt transfer is described most particularly in U.S. Pat. No. 2,911,280 (Cicogna). A special release paper is prepared bearing a coating of waxy materials capable of being printed with an ink similarly constituted but containing dyes appropriate to the textile to be decorated. The printed design is applied to the textile by passing paper and fabric together through a hot calender so that transfer takes place at 150.degree. C. and 100-150 kg/sq.cm. The ink binding substances melt under these conditions and are forced into the interstices of the fabric. In order to fix the dyes the fabric is impregnated before transferring with necessary chemicals and the fabric is steamed after transfer. Special agents are incorporated into the ink to assist the necessary removal of the waxy substances after steaming and this stage removes also any unfixed dye. An improvement of this procedure so as to assist the initial printing process for the production of the paper is described in Dutch Patent Application 7302988 (Dai Nippon Printing Co. Ltd) which incorporates special agents giving greater control over the melting of the ink layer. Although this procedure gives rapid transfer and avoids the problems consequent upon the slow transfer found in sublimation and solvent transfer, melt transfer utilises materials which have to be removed from the fabric at the end of the process. In addition the need to produce a melting system precludes the simultaneous application of dye fixation assistants. Furthermore the process is suitable only for dyes to be fixed by wet processing so that pigment binding and disperse dyes applied by dry heat are excluded.
U.S. Pat. No. 4,021,591 describes iron-on transfers using a polymeric hot-melt layer to transfer the image and bond it to the fabric to be decorated. Such transfers as are described therein are harsh and give an adverse feel to the decorated fabric, see column 5 line 42 to column 6 line 45, where the feel is from "soft leathery" to "relatively stiff or hard". In many applications any increase in stiffness or hardness or feel of the fabric is undesirable.
The purpose of the present invention is to provide a method whereby the several disadvantages of the above methods may be avoided to provide a simpler and more convenient procedure which is based on a different and more effective principle, that of film release transfer. Transfers using this principle are known. For example British Patent No. 1,320,400 (Trentes aux-Toulemonde) describes a hot pressure film release system for the decoration of plastic surfaces. U.S. Pat. No. 3,519,456 (Reed) describes a tacky film release system for transferring images to a receptor surface. However in both of these and related cases it is desired to preserve the transferred film as such on the receptor surface. When the latter is a textile material or a material the surface of which it is undesirable to modify, then the application of a coherent film to it is generally undesirable as the handle, drape, permeability and feel are undesirably modified. In addition a coherent film consisting of a thermoplastic material makes it impossible for the consumer to iron or dry press the article.
Indeed it is a fundamental disadvantage of the majority of prior art decoration processes that the decorated design is present as a more or less continuous film having a very easily perceptible filmy feel to the decorated surface. Thus British Patent Specification No. 1,221,649 discloses a method of applying a pattern to a textile material which comprises transferring a resinous coating under the action of heat and pressure to a textile. Such resinous coatings are thick, typically 75 microns thick, and although the layer is subsequently heated and the resin caused to flow between the fibres of the textile material, the original handle and softness of the material are simply not maintained, despite the assertion in Specification No. 1,221,649 to the contrary.
Likewise, decorating fabrics using transfer films as described in U.S. Pat. No. 2,556,078 does not maintain the original handle and feel of the fabric surface. As noted at column 5 lines 66 to 68 of that specification, the typical thickness of the layer applied is 25 to 50 microns.
We have now found that the original softness, handle and feel of the fabric may be retained by the use of certain selected polymeric materials as a basis for a transferable decoration film and additionally by ensuring that the film is laid down at such a thickness that it may first of all be applied under the action of heat and pressure to a fabric surface and thereafter caused by a subsequent heat treatment to break up into discrete sections. The physical properties of the film forming material and the thickness of the film layer must both be correct in order to achieve the satisfactory and improved results provided by the present invention.